JP2003272844A - Dimming method of organic el panel, and organic el panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively dim a luminescent spot defective pixel. <P>SOLUTION: Organic layers (hole transport layer 52, organic light emitting layer 54, electron transport layer 56) of the organic EL element are deteriorated and light emitting function is eliminated by selectively irradiating a laser beam to an organic EL element of a pixel. The laser beam is irradiated to the limited part (central part) of a light emitting part. By the above, the laser beam is not irradiated to the part where the thickness is changing, and the damage of a negative electrode 58 is effectively prevented. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming method for dimming defective pixels of an organic EL panel.

[0002]

2. Description of the Related Art Conventionally, an organic EL display panel has been known as one of flat display panels. Unlike the liquid crystal display panel (LCD), this organic EL display panel is self-luminous, and its spread is expected as a bright and easy-to-see flat display panel.

This organic EL display is provided with organic EL elements in pixels and arranged in a matrix in a large number. Further, as a driving method of the organic EL element, there are a passive method and an active method as in the LCD, but it is said that the active matrix method is preferable as in the LCD. That is, the active matrix method in which a switching element is provided for each pixel, and the switching element is controlled to control the display of each pixel is higher than the passive method in which the switching element is not provided for each pixel. It is preferable because a fine screen can be realized.

In the case of an LCD, one switching element (TFT) is used, and this is directly connected to the pixel electrode, but in the case of an organic EL panel, two TFTs and 1
One capacity is used. FIG. 8 shows a configuration example of a pixel circuit in an organic EL panel using a conventional thin film transistor (TFT). The organic EL panel is configured by arranging such pixels in a matrix.

The gate of the first TFT 10, which is an n-channel thin film transistor selected by the gate line, is connected to the gate line extending in the row direction. A data line DL extending in the column direction is connected to the drain of the first TFT 10, and a storage capacitor CS having the other end connected to a capacitor line SL which is a low-voltage power supply is connected to the source thereof. The connection point between the source of the first TFT 10 and the storage capacitor CS is connected to the gate of the second TFT 40 which is a p-channel thin film transistor.
The source of the second TFT 40 is the power supply line VL.
And the drain is connected to the organic EL element EL. The other end of the organic EL element EL has a cathode power source C.
Connected to V.

Therefore, when the gate line GL is at H level, the first TFT 10 is turned on, and the data of the data line DL at that time is held in the holding capacitor CS. And
The current of the second TFT 40 is controlled according to the data (potential) maintained in the storage capacitor CS, and the second TFT 40
According to the current of 40, a current flows through the organic EL element EL to emit light.

Then, when the first TFT 10 is turned on, a video signal corresponding to the pixel is supplied to the data line DL. Therefore, the storage capacitor CS is charged according to the video signal supplied to the data line DL, whereby the second TFT 40 causes a corresponding current to flow and the organic EL
The brightness control of the element EL is performed. That is, the second TFT
The gradation display of each pixel is performed by controlling the gate potential of 40 to control the current flowing through the organic EL element.

In such an organic EL panel, the first TFT 10 or the second TFT 40 provided for each pixel is provided.
May be defective. In the case of a defect in which the TFT is fixed so as to turn off the current to the organic EL element, the pixel only becomes a dark spot, and even if there is one dark spot among the bright spots, it is visible. It's not a tough problem. On the other hand, in the case of a defect in which the current to the organic EL element is always on, the pixel becomes a bright spot. If even one pixel has a bright spot when the surrounding pixels display black, this is inconvenient because it is visually recognized by the observer. Therefore, as for a defective pixel which becomes a bright spot, a process for darkening the defective pixel has been conventionally performed.

That is, an organic E having a predetermined number of dark spots
This is because the L panel has no problem as a product and the yield can be significantly improved by reducing the bright spots.

Here, this darkening can be performed by breaking the wiring leading to the pixel. That is, as in the case of the LCD, the second TFT 40 is driven by the YAG laser or the like.
It is conceivable to disconnect the wiring between the power supply line and the pixel electrode.

As a result, the bright spots can be turned into dark spots, and the problem in the overall display can be solved.

[0012]

However, if the dark-spotting process is performed by the YAG laser, the cathode may be damaged and the display of other pixels may be affected. That is, in the case of an active matrix type organic EL panel,
A TFT is formed on a glass substrate, an ITO anode is formed above the TFT, an organic layer such as a hole transport layer, an organic light emitting layer, and an electron transport layer is stacked on the TFT, and a metal cathode is formed thereon. Is formed. As described above, a part of the organic layer and the cathode exist above the TFT. In particular, the cathode is formed as a common electrode over almost the entire surface of the panel.

Therefore, when the wiring of the TFT is cut by the YAG laser, the laser reaches the cathode and the cathode is also ablated. Therefore, the cathode has a structure with a hole in that portion. Further, this ablation may change the quality of the cathode, which may affect the display of peripheral pixels. Further, the cutting by the laser is to evaporate and fly the substance existing there, and the side surface of the organic layer of the organic EL element is directly exposed to the space above the cathode. Therefore, deterioration of the organic layer due to infiltration of moisture from the exposed portion is likely to proceed, and defective pixels may spread.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for dimming an organic EL panel capable of effectively dimming defective pixels.

[0015]

SUMMARY OF THE INVENTION The present invention is a method of dimming a defective pixel of an organic EL panel, which comprises irradiating a laser on a part of a light emitting region of the defective pixel, In the organic EL device, the light emitting ability is deteriorated to reduce the light.

As described above, according to the present invention, the light emission capability of the defective pixel is deteriorated by the irradiation of the laser beam, and the light can be reduced. Therefore, unlike the cutting of wiring by a strong laser, the cathode is not damaged. Therefore, there is no adverse effect due to cathode damage, and the bright spot defective pixels can be dimmed. In particular, damage to the cathode can be effectively prevented by making only a part of the light emitting region, not the entire light emitting region, the target of dimming.

It is preferable that the dimming region is a region excluding the peripheral portion of the light emitting region. The peripheral region of the light emitting region is a place where the layer thickness and the like change, and the laser in this portion is likely to be non-uniform, and the cathode is easily damaged. By not irradiating the peripheral portion of the light emitting portion with laser, it is possible to reliably prevent damage to the cathode.

Further, the present invention relates to an organic EL panel in which defective pixels are dimmed by the above-described dimming method, whereby a bright spot can be made a dark spot without adverse effects due to cathode damage. it can.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, a UV (short wavelength) laser such as an excimer laser is used as a light source, and the laser is irradiated to the defective pixel. As a result, the organic layer of the defective pixel is deteriorated, the light emitting capability is deteriorated, and dimming can be performed.

That is, the laser irradiation is not so strong as to evaporate the irradiated layer, and the laser irradiation causes the laser to be absorbed in the organic layer, which causes heat deterioration in a very short time and the light emitting ability. It goes out and dimming is performed.

In particular, the laser does not have enough energy to damage the cathode and there is no damage to the cathode. Therefore, there is no adverse effect due to cathode damage, and the bright spot defective pixels can be dimmed.

Originally, the organic material of an organic EL element is weak to heat and the like, and the light emitting ability is easily deteriorated. In the present embodiment, a reaction similar to this deterioration is promoted by irradiating the organic layer of the device with a laser to reduce the light.
It is considered that the organic layer is annealed by the laser irradiation and causes deterioration of the hole and electron transporting ability and the light emitting performance of the organic light emitting material. The molecular structure itself does not change,
It is also possible that the membrane structure is altered. It should be noted that the display defects due to the alteration of the organic layer, which usually occurs, spread with the passage of time. However, when the laser is irradiated and the light is dimmed as in the present embodiment, the dimmed region hardly expands outside the laser irradiation region. Therefore, the repair of defects can be performed more reliably, and high display quality can be maintained.

Here, the YAG laser includes 266 and 35.
Although there are 5,532,1064 nm, etc., the YAG laser of 266 nm cannot pass through the acrylic flattening film or the like, and the effect is small. Also, with a YAG laser of 532 nm or more, the effect cannot be obtained unless the power is made extremely large, and in this case, the cathode is also affected.

On the other hand, the 355 nm YAG laser is preferable because it can efficiently deteriorate the light emitting ability due to the alteration of the organic layer without affecting the cathode. Further, there is an excimer laser having a wavelength of 308 nm, which is also suitable.

FIG. 1 shows a pixel configuration. Here, on the element substrate, the TFT 10 shown in FIG.
40, a capacitor CS and an organic EL element EL are formed,
In this figure, the second TFT 40 and the organic EL element E
Only L is shown.

In the figure, the element substrate is a glass substrate 30.
It has the 2nd TFT40 formed on it. This second
The configurations of the TFT 40 and the organic EL element EL are shown. Thus, the second TFT 40 is formed on the glass substrate 30, and the second TFT 40 has the active layer 40a made of low temperature polysilicon. Both ends of the active layer 40a are a source region and a drain region doped with impurities, and a central portion sandwiched between them is a channel region. A gate electrode 40c is formed above the channel region via a gate insulating film 40b made of silicon oxide.
Are formed. The gate insulating film 40b and the gate electrode 40c are covered with the interlayer insulating film 34, and on both sides of the gate electrode 40c, the source electrode 40d connected to the source region and the drain region via the contact hole of the interlayer insulating film 34, The drain electrode 40e is formed. The upper ends of the source electrode 32d and the drain electrode 32e are located on the surface of the interlayer insulating film 34.

Further, on the surface of the interlayer insulating film 34, a metal wiring or the like connecting the drain electrode 40e and the power supply line VL is arranged. Further, a first flattening film 36 is formed so as to cover the interlayer insulating film 34.

On the upper surface of the first flattening film 36, I
A transparent electrode 50 composed of TO is formed, and one end of the transparent electrode 50 passes through the contact hole of the first planarization film 36 to form the second TF.
It is connected to the source electrode 40d of T40.

The transparent electrode 50 constitutes the anode of the organic EL element, and the metal cathode is formed on the transparent electrode 50 via the hole transport layer 52, the organic light emitting layer 54 and the electron transport layer 56. 58 is formed. A second flattening film 60 is arranged around and on the side of the transparent electrode 50.
Further, the organic light emitting layer 54 is larger than the transparent electrode 50 in order to cope with the positional deviation at the time of formation, but extends over the second planarization film 60 so that it exists only in the pixel region, but immediately terminates. is doing. On the other hand, the hole transport layer 52 and the electron transport layer 56 other than the organic light emitting layer 54 are formed so as to spread over the entire surface. However, the electron transport layer 56 may include a material that emits light such as Alq3, and the electron transport layer 56 is often limited to only the light emitting portion, like the organic light emitting layer 54.

In such an organic EL panel, the bright spot defect pixel is irradiated with a short wavelength laser from the glass substrate 30 side to selectively damage the organic layer of the pixel to reduce the light.

A pulsed laser is usually used as the laser, but continuous light may be used. The irradiation amount depends on the type of the glass substrate, the organic layer, the material of the other layers, etc., but it is preferable to experimentally determine the irradiation amount so that the dark spot can be surely formed and the cathode is not damaged.

That is, as shown in FIG. 2, a test panel is prepared (S11), the irradiation amount is changed, and a plurality of pixels are irradiated with laser (S12). Then, the result of this laser irradiation test is evaluated (S13). That is, it is evaluated whether or not dark spots are formed and the cathode is damaged. And you can surely make a dark spot,
In addition, the condition that damage to the cathode is not detected is determined (S
14).

In this way, when the conditions are determined, the conditions are adopted and the dark spot conversion processing is performed on the bright spot defective pixels of the actually manufactured organic EL panel (S1).
5).

As described above, by the laser irradiation, it is possible to perform the dark spot forming process for the pixel without damaging the cathode.

Note that the mask which is placed immediately before the glass substrate 30 (may be in contact with it) limits the laser irradiation area to the pixels which are darkened. However, if the laser irradiation range can be surely limited, the laser irradiation range may be limited by the optical system. Further, the laser irradiation may be applied only to the light emitting region. Therefore, it is preferable to irradiate the laser only on the portion where the organic light emitting layer 54 exists.
Generally, there is no organic light emitting layer 54 in the portion where the TFT exists. Therefore, by limiting the laser irradiation range to the region where the organic light emitting layer 54 exists, the laser irradiation to the TFT can be avoided. The TFT has an active layer of low temperature polysilicon and laser irradiation is less preferred, preferably not. Even if the organic light emitting layer 54 exists above the TFT, it is also preferable that the TFT is not irradiated with the laser.

[Attenuation of Part of Pixel] In the present embodiment, the light emitting portion is not entirely dimmed, but is partially dimmed. That is, as a result of studying the occurrence of damage on the cathode, it was found that the damage on the portion corresponding to the end of the anode was large. As shown in FIG. 1, at the end of the anode 50, the shape of each layer changes in a complicated manner. Therefore, it is considered that when the laser is irradiated, the light reaching the cathode 58 is not uniform, and a part of the light becomes strong and is likely to be damaged.

Therefore, in this embodiment, laser irradiation is performed while avoiding the peripheral portion of the anode 50. That is, as shown in FIG. 4, a range narrower than the anode 50, more specifically, the anode 5
Laser is emitted in a range narrower than a light emitting region formed in a region where 0 and the cathode 58 face each other with at least the light emitting layer 54 interposed therebetween. As a result, damage to the cathode 58 can be effectively avoided.

If the light emitting layer 54 has a concave portion, it is not necessary to irradiate the concave portion with laser.
Further, there are various shapes of the anode. Therefore, as shown in FIG. 5, the laser irradiation range may be set according to the shapes of the light emitting layer and the anode.

Further, when the irradiation range is limited by a mask or the like, it is not preferable to have a complicated shape. Therefore,
As shown in FIG. 6, a relatively small unit irradiation range may be set and the light emitting region may be dimmed by laser irradiation a plurality of times. As described above, if the unit irradiation range is reduced, it is possible to flexibly cope with the change of the shape of the irradiation region, and the versatility of the repair apparatus is enhanced.

As described above, according to the present embodiment, the entire light emitting region is not dimmed, and a region that is not dimmed remains in the peripheral portion of the light emitting region. However, this area is also small in area and the amount of light emission is small. In particular,
Light emission in the central portion of the light emitting region is suppressed. Therefore,
The brightness as a pixel is considerably low, making it difficult to be visually recognized. Therefore, by such dimming,
It is possible to reliably prevent the occurrence of damage to the cathode and achieve effective dimming of bright spot defective pixels.

Here, FIG. 7 shows a planar structure of one pixel of the organic EL panel. The gate line GL extends in the horizontal direction, and the gate 2 of the first TFT 10 is connected to the gate line GL.
Are connected. The first TFT 10 is a double gate type in which two gates 2 are provided. This first
One end (source) of the active layer 6 of the TFT 10 is connected to the data line DL. The other end of the active layer 6 has a capacitance C
It is connected to the lower electrode of S or also serves as the lower electrode. The active layer 6 is a channel region below the gate 2 of the first TFT 10, the region sandwiched between the two gates 2 is the drain and the source, and the region connected to the lower electrode of the capacitor CS is the source. .

An upper electrode (substantially the same layer as the gate electrode) is arranged so as to face the lower electrode of this capacitor CS via a silicon oxide film, and the capacitor CS is formed by these lower electrode, dielectric and upper electrode. Has been formed. The upper electrode of the capacitor CS is connected to the capacitor line SL maintained at a low potential.

Therefore, when the gate line GL becomes H level, the first TFT 10 is turned on, and the voltage of the data line DL is written (charged) in the capacitor CS.

The lower electrode of the capacitor CS is connected to the gate 25 of the second TFT 40. The second TFT 40 is composed of two second TFTs 40-1 and 40-2 connected in parallel, with both ends serving as a source and the center serving as a drain. That is, the second TFT 40 has the active layer 16, and the sources 16s-1 at both ends of the active layer 16 are
16s-2 is connected to the power supply line VL. Also, channels 16c-1 and 16c- are located below the gate 25.
2, and the drains 16d-1 and 16d-2 are formed in the center.

Then, the drains 16d-1 and 16d
-2 is connected to the organic EL element EL by the wiring 41. That is, the second TFTs 20-1 and 20-2 in FIG.
The drains 16d-1 and 16d-2 of 0-2 are connected to the anode 50 of the organic EL element.

In such a pixel, as described above,
By irradiating with a UV laser while avoiding the peripheral portion of the anode 50, dark spots can be formed in the pixels.

"Pixel Dimming" As described above, a defective pixel can be darkened. Here, if such darkening is performed, the cathode may be damaged. That is, depending on the organic EL panel, in S14,
In some cases, it may not be possible to select the condition for surely stopping the dark-spotted light emission without damaging the cathode.

In such a case, although no dark spot is formed,
Select the dimming condition. That is, the light emission amount is not 0, but the condition is low and the brightness is quite dark.

For example, as shown in FIG. 3, a test panel is prepared (S21), the irradiation amount is changed, and a plurality of pixels are irradiated with laser (S22). Then, the condition that the cathode is not damaged is selected (S23). Then, among them, the one whose light emission amount is less than or equal to a predetermined value is selected (S2
4). If there are a plurality of selected ones, the one that emits as little light as possible is selected (S25).

In this way, it is possible to reduce the brightness of the pixel having the bright spot defect. A defective pixel that has undergone dimming emits light, but it is not visible in normal use. That is, even if it is visible in a completely dark room, it will not be visible if the surroundings are bright to some extent. Depending on the size of one pixel, if the amount of light emission is 20% or less when one pixel is several 10 μm square,
It's not too noticeable. Further, in the test using the ND filter, if the light emission amount is recognized as a dark spot, there is no problem at all, and the light may be reduced to the extent that it is recognized as a low bright spot.

As described above, according to this embodiment, the light emission amount of the bright spot defective pixel is reduced. Therefore, it is possible to reliably prevent the cathode from being damaged and to process the defective pixel. The mechanism may be that the organic layer itself is altered, the interface between the organic layer and the organic layer is altered, or the interface between the organic layer and the electric machine is altered.

[0053]

As described above, according to the present invention,
The light emitting ability of the defective pixel is deteriorated, and dimming can be performed. Therefore, unlike the cutting of the wiring by the laser, the cathode is not damaged. Therefore, there is no adverse effect due to cathode damage, and the bright spot defective pixels can be dimmed.

Further, by selectively irradiating the organic EL element in the area of the defective pixel with light, particularly laser,
It is possible to effectively change the quality of the organic layer of the defective pixel.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a pixel.

FIG. 2 is a flowchart showing an example of laser irradiation amount setting.

FIG. 3 is a flowchart showing another example of setting a laser irradiation amount.

FIG. 4 is a diagram showing an example of a laser irradiation region.

FIG. 5 is a diagram showing another example of a laser irradiation region.

FIG. 6 is a diagram showing still another example of a laser irradiation region.

FIG. 7 is a diagram showing a planar configuration of a pixel.

FIG. 8 is a diagram showing a configuration of a pixel circuit.

[Explanation of symbols]

10 First TFT, 40 Second TFT, 50 Anode.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Ogawa             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F-term (reference) 3K007 AB08 AB11 AB18 DB03 FA00

Claims (3)

[Claims] 1. A dimming method for dimming a defective pixel of an organic EL panel, comprising irradiating a laser to a partial region of a light emitting region of the defective pixel to determine the light emitting ability of the organic EL element in this region. A method for dimming an organic EL panel that deteriorates and dims. 2. The method for dimming an organic EL panel according to claim 1, wherein the region to be dimmed is a region excluding a peripheral portion of a light emitting region. Light conversion method. 3. An organic EL panel, wherein defective pixels are dimmed by the method for dimming an organic EL panel according to claim 1.